1. Field of the Invention
The present invention relates to an improved injection molding apparatus and method whereby a relatively flexible mounting assembly is provided for mounting a relatively movable injection unit with respect to a relatively stationary unit base.
2. Description of Related Art
In some multi material injection molding applications, a second injection unit is coupled to a movable platen. In such applications, the second injection unit is coupled to a sub plate which moves along a stationary structure (such as rails) as the moving platen moves back and forth. However, the heat generated during the molding operation often causes thermal elongation of the heated components in the sub plate sand the stationary structure, leading to misalignment of the injection unit with respect to the rails. This may restrict the movement of the injection unit or even cause a failure of the coupling parts.
U.S. Pat. No. 4,243,362 to Rees and U.S. Pat. No. 4,444,711 to Schad both disclose multi-material turret injection molding machines having one of their two injection units mounted on the machine's movable platen and directly connected to that portion of the mold that is mounted to the movable platen with a conventional sealing nozzle/bush interface.
Japanese Publication 61-121912 to Shoichi discloses a multi-material injection molding machine having two injection units that connect to hot runners mounted within intermediate movable platens via nozzles.
PCT publication WO 02/22340 to Schuett discloses an injection molding machine having a single injection unit slidably mounted alongside and parallel to the clamp mechanism that is releasably sealed to the molds' infeeding ports by a cylinder that also maintains the sealed relationship throughout the molding cycle.
Thus, what is needed is structure and method for movably coupling the relatively moving injection unit to the relatively stationary support structure in such a way as to minimize any misalignment, part stress, or failure caused by the movement.